Liquid crystal display device and manufacturing method therefor

ABSTRACT

A liquid crystal display device including gate wiring or a gate electrode formed on a substrate on a TFT side of the TFT liquid crystal display device, wherein the wiring or the electrode has a structure of being held between two different insulation layers or insulators, and the structure is comprised of a first layer mainly consisting of copper and a second layer consisting of an oxide covering an outer circumferential part of the first layer, further, the second layer has compositional formula of Cu x Mn y Si z O (0&lt;X&lt;Y, 0&lt;Z&lt;Y).

TECHNICAL FIELD

The present invention relates to a liquid crystal display device provided with gate wiring mainly consisting of copper (Cu) covered with an oxide film containing Mn (Mn-containing oxide film) and to a manufacturing method therefor.

BACKGROUND OF INVENTION

In recent years, a low-power-consumption liquid crystal display device (LCD) that is thin, lightweight, and capable of being driven by lower voltage has been widely used. In such a liquid crystal display device, a screen size has been increasing year after year and a display of moving images just like TV images has been required. To meet such requirements, wiring should be configured with a low-resistive and high-conductive material.

Along with such increase in the screen size of the liquid crystal display device, a gate wiring material has been changed from molybdenum alloy to aluminum alloy or aluminum clad. However, aluminum (Al) has problems of hillock and electromigration.

For example, as disclosed in Patent Document 1, Japanese published unexamined patent application No. 2000-199054, a wiring material consisting of Al—Nd alloy has been proposed, and anodized Al, Mo-alloy-cladded Al, or double-layered Al has been used. The Al—Nd alloy has a resistivity of 5.1 μΩ·cm while pure Al has a resistivity of 2.5 μΩ·cm.

Therefore, in order to use pure Al in practice, wiring having a three-layered structure of Ti/Al/Ti or Mo/Al/Mo is used as measures for the hillock and electromigration. However, this causes an increase in film formation steps, which remains as a problem.

On the other hand, copper has drawn attention as a material having resistivity lower than those of the above-described gate electrode materials. However, copper has problems of not only poor adhesiveness to glass used as a TFT substrate in an LCD, but also of being easily oxidized when an insulation layer is formed.

For this reason, a technique using alloyed copper wiring has recently been attempted in a TFT-LCD in order to solve such problems. This technique is intended to make an alloying element form reaction products with a substrate to thereby ensure adhesiveness to the substrate as well as to make an additive element form oxide on the Cu surface to thereby make the oxide act as an oxidation resistant film for Cu.

However, with this proposed technique, intended characteristics have not been adequately developed. That is, electrical resistance of Cu becomes higher because the alloying element remains in Cu, and therefore advantages over wiring materials using Al or Al alloy have not been able to be exhibited.

Further, as described in Patent Document 2, Japanese published unexamined patent application No. 2004-163901, in order to use the copper wiring for a TFT-LCD, a technique to ensure adhesiveness and barrier characteristics to a substrate by the formation of a Mo alloy film between Cu and the substrate has been considered.

However, this technique has problems of an increase in process steps, i.e., a step of forming the Mo alloy film, as well as of an increase in wiring effective resistance. Further, a Cu single layer is used for source and drain electrodes, however, there remains a problem in its stability.

Also in Patent Document 3, Japanese published unexamined patent application No. 2004-139057, a technique in which a refractory nitride such as TaN, TiN, or WN is formed around Cu is proposed to solve such problems regarding the Cu wiring. However, compared with the conventional wiring materials, this technique has disadvantages of requiring another material to form a barrier layer and additional process steps, and of increasing effective resistance of wiring because a high-resistive barrier layer is thickly formed.

Further, Patent Document 4, Japanese published unexamined patent application No. 2005-166757 discloses a method for improving adhesiveness and oxidation resistance by the addition of one or more elements selected from Mg, Ti, or Cr to TFT-LCD wiring. However, this technique has a problem that the additive element remains in the wiring, causing an increase in wiring resistance. Also, the additive element reduces oxide in a substrate and the reduced element is diffused in the wiring, causing a problem of an increase in the wiring resistance.

Patent Document 5, Japanese published unexamined patent application No. 2002-69550 discloses a method for improving oxidation resistance by the addition of 0.3 to 10 wt. % of Ag to Cu. However, this technique has problems that adhesiveness to a glass substrate is not improved and oxidation resistance sufficient to resist liquid crystal processing cannot be obtained.

Patent Document 6, Japanese published unexamined patent application No. 2005-158887 proposes copper alloy prepared by the addition of 0.5 to 5 wt. % of at least one element of Ti, Mo, Ni, Al, or Ag to Cu to improve adhesiveness. However, there is a problem of an increase in electrical resistance of wiring due to the additive element.

Patent Document 7, Japanese published unexamined patent application No. 2004-91907, proposes a method for suppressing oxidation by the addition of 0.1 to 3.0 wt. % of Mo to Cu followed by the segregation of the added Mo at grain boundaries. However, although this technique is capable of improving oxidation resistance of Cu, it has a problem of an increase in wiring resistance.

In Patent Document 8, WO2006-025347, copper alloy prepared by the addition of an appropriate element to Cu is used, wherein the additive element forms an oxide film to become a passivation film, which suppresses oxidation of Cu, and the passivation film is also formed at an interface with an adjacent insulation layer, which suppresses interdiffusion. Consequently, copper wiring having high conductivity and superior adhesiveness to a substrate is provided. Further, a liquid crystal display device using such copper wiring is provided. In addition, it is suggested that one of such additive elements preferably be Mn.

In Patent Document 9, Japanese granted patent publication No. 3302894, a TFT structure used in TFT-LCD is proposed and a TFT structure, wherein a gate electrode coated with an oxide film when a Cu alloy is applied to the gate electrode, is specifically presented. In the document, it is presented that when Cu is a first metal, the second metal is at least one type chosen from Ti, Zr, Hf, Ta, Nb, Si, B, La, Nd, Sm, Eu, Gd, Dy, Y, Yb, Ce, Mg, Th, and Cr. However, the additive element of this second metal is different from that of the current invention.

As described above, in these conventional techniques, an attempt to ensure adhesiveness to a substrate and oxidation resistance by the addition of an alloying additive element to Cu has been made, however, none of them has achieved a satisfactory result.

Especially, although Patent Document 8, WO2006-025347, suggests a liquid crystal display device using such copper wiring, the suggested technique alone is not able to provide a satisfactory configuration to realize a gate wiring structure to be used for the liquid crystal display device. Also, in the Patent Document 9, the oxide film for coating the gate electrode is specified as the oxide film mainly comprising the second metal formed by thermally treating in an oxygen ambient, however, it is not only unexplained but also not even indicated in the Patent Document 9 that the thermal treatment reacting Cu alloy and Si oxide film in contact with the Cu alloy, thereby forming oxide film of gate electrode, which ensures adhesiveness with a substrate.

That is, all the difficulties in forming a Cu alloy film with less process steps, lowering effective resistance of wiring, and improving adhesiveness to a glass substrate must be solved, however, with the above conventional techniques, these difficulties cannot be solved, and product manufacturing is practically difficult.

The present invention has been made in consideration of such situations, and it is therefore objects of the present invention to form an oxide film having high adhesiveness to a substrate to thereby prevent oxidation of a wiring material or the like, and also to provide a liquid crystal display device provided with wiring, an electrode or a terminal electrode having high conductivity, and a manufacturing method therefor. Further, another object of the present invention is to form the wiring, electrode, or terminal electrode applicable to practical manufacturing processing while simultaneously accomplishing all the above objects.

BRIEF SUMMARY OF THE INVENTION

In order to accomplish above objects, the present invention, a liquid crystal display device comprising gate wiring or a gate electrode formed on a substrate on a TFT side of the TFT liquid crystal display device, wherein the wiring or the electrode has a structure of being held between two different insulation layers or insulators, and the structure is comprised of a first layer mainly consisting of copper and a second layer consisting of an oxide covering an outer circumferential part of the first layer, further, the second layer has compositional formula of Cu_(X)Mn_(Y)Si_(Z)O (0<X<Y, 0<Z<Y).

This first layer is formed from a copper alloy, and an additive element in the copper alloy may be at least one type of metal selected from the group consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd.

Alternatively, the first layer is formed from a copper alloy, and an additive element in the copper alloy may be Mn.

An additive amount of Mn may be in a range of 0.5 to 25 atomic %.

The second layer may further be an oxide layer further containing Mn mainly and Cu subsidiarily.

The insulation layer comprising said wire or said electrodes, or the insulation film may contain glass.

The insulation layer comprising said wire or said electrodes, or the insulation film may be any one selected from the group consisting of SiN_(X), SiO_(X), and SiO_(X)N_(Y).

The second layer may contain Cu and Si.

Film thickness of the second layer may be 1-30 nm.

A common electrode may be formed on the TFT substrate side on which the gate wiring is formed, in the TFT liquid crystal display device.

A liquid crystal display device being a TFT liquid crystal display device comprising a liquid crystal material held between a pair of substrates, wherein gate wiring or a gate electrode formed on a side of a TFT substrate of the pair of substrates held by two different insulation layers containing Si has a wiring structure, in which gate wiring or a gate electrode is covered with an oxide and a layer mainly consisting of Cu and added with Mn, the other in the wiring structure has a compositional formula of Cu_(X)Mn_(Y)Si_(Z)O (0<X<Y, 0<Z<Y), and the wiring structure is formed in a shape in which the one in the wiring structure is covered with the other.

The other in the wiring structure may be an oxide layer containing Mn mainly and Cu subsidiariy.

The thickness of second layer may be 1 to 30 nm.

A common electrode may be formed on the TFT substrate side on which the gate wiring or the gate electrode is formed, in the above-mentioned TFT liquid crystal display device.

An organic EL display device, wherein a scanning line formed on one of substrates of the organic EL display device has a structure of being held between two different insulation layers or insulators, and the structure is comprised of a first layer mainly consisting of copper and a second layer consisting of an oxide covering an outer circumferential part of the first layer.

A compositional formula of the second layer may be CuXMnYSiZO (0<X<Y, 0<Z<Y).

The second layer may be an oxide layer further containing Mn mainly and Cu subsidiary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram of a cross-section of a TFT (Thin Film Transistor) type liquid crystal display (LCD) module to which the features of the present invention are applied.

FIG. 2 is a conceptual diagram of a cross-section of a part of the TFT-LCD panel shown in FIG. 1.

FIG. 3 is a conceptual diagram of an IPS (In-Plane Switching Nematic) type liquid crystal in which a common electrode is placed on the opposite side compared to the TFT-LCD panel shown in FIG. 2.

FIG. 4 is a plan view of a pixel part and a TFT part of the TFT-LCD panel shown in FIG. 2.

FIG. 5 is a cross-sectional view of a pixel part and a TFT part shown in FIG. 4.

FIG. 6 is an equivalent circuit diagram of a pixel part and a TFT part shown in FIG. 4.

FIG. 7 is a cross-sectional view of a TFT (staggered top gate structure) to which the features of the present invention are applied.

FIG. 8 is a cross-sectional view of a TFT (inversely staggered channel stopper structure) to which the features of the present invention are applied.

FIG. 9 is a cross-sectional view of a TFT (inversely staggered channel etch structure) to which the features of the present invention are applied.

FIG. 10 is one example (1) of a cross-section of a pixel part and a TFT part embodying the features of the present invention for manufacturing a liquid crystal display.

FIG. 11 is a graph illustrating the change of the electrical resistivity (1) of the copper alloy (Cu—Mn) embodying the features of the present invention when thermally treated in various atmosphere.

FIG. 12 is a graph illustrating the change of the electrical resistivity (2) of the copper alloy (Cu—Mn) embodying the features of the present invention against thermal treatment temperature using a thermal temperature time period as a parameter.

FIG. 13 illustrates a typical operating waveform diagram of a TFT.

FIG. 14 illustrates a model of a propagation delay of a gate voltage pulse.

FIG. 15 illustrates an example of the adhesion strength of the copper alloy (Cu—Mn) embodying the features of the present invention measured by nanoscratch test, comparing with a case of forming Ta frequently used in semiconductor wiring.

FIG. 16 is a composition diagram of a wiring structure embodying the features of the present invention.

FIG. 17 is an enlarged view of a composition of a wiring structure across the interface between Cu and SiO2 embodying the features of the present invention.

FIG. 18 is a cross-section TEM picture after thermally treating the Cu—Mn alloy embodying the features of the present invention on the glass at 250° C. for 10 minutes.

FIG. 19 is a result of adhesiveness evaluation by tape test after thermally treating Cn—Mn alloy embodying the features of the present invention formed on a glass substrate at each temperature for predetermined time.

FIG. 20 illustrates the time-variation in the resistivity of the Cu—Mn alloy thin film embodying the features of the present invention that was thermally treated at 350° C., and the time variation in the thickness of Mn oxide formed on the Cu surface.

FIG. 21 is a diagram illustrating the fundamentals of a TFT manufacturing process to which the features of the present invention are applied.

FIG. 22 is a diagram illustrating a five-mask process in TFT manufacturing to which the features of the present invention are applied.

FIG. 23 is a cross-sectional view of a TFT manufactured by the five-mask process to which the features of the present invention are applied.

FIG. 24 is a cross-sectional view of an electrode led outside of a TFT manufactured by the five-mask process to which the features of the present invention are applied.

FIG. 25 is a plan view of a pixel part of a TFT manufactured by the five-mask process to which the features of the present invention are applied.

FIG. 26 is a cross-sectional photograph of an oxide film layer for wiring embodying the features of the present invention.

FIG. 27 is a diagram illustrating a composition of an oxide film layer for wiring embodying the features of the present invention.

FIG. 28 is a film thickness of an oxide layer embodying the features of the present invention against thermal treatment time period using a thermal temperature as a parameter.

FIG. 29 is diagram of a cross-sectional model of a wiring structure according to the present invention.

FIG. 30 is one example of a cross-section of an organic EL element embodying the features of the present invention.

FIG. 31 is one example of an equivalent circuit diagram of a pixel in an organic EL display embodying the features of the present invention.

FIG. 32 is one example of a cross-section of an organic EL display embodying the features of the present invention.

DETAILED DESCRIPTION OF INVENTION

Embodiments of the present invention will hereinafter be described with reference to drawings. In the embodiments, a technique in which copper alloy of the present invention is applied to wiring constituting each electrode and a matrix of an a-Si TFT on a TFT substrate is described. First, a liquid crystal display device used for the present invention is described below.

FIG. 1 is a conceptual diagram illustrating a cross-section of a liquid crystal display (LCD) module. A display size of a liquid crystal display device has been increasing, and consequently an active matrix LCD is utilized. One representative of such LCDs is a TFT-LCD in which an LCD is driven by thin film transistors (TFTs). FIG. 1 represents such a TFT-LCD module. The TFT-LCD module is comprised of an LCD panel 1, a driving circuit 2, a backlight 3, and chassis 4. The LCD panel 1 consists of a TFT substrate 11 and a color filter (CF) substrate 12, which are arranged on lower and upper sides respectively.

The driving circuit 2 serves to externally apply electrical signals to the LCD panel 1 to drive it. The driving circuit 2 is comprised of an LCD driver LSI chip 21 or an LCD driver LSI multilayered printed circuit board (PCB) 22, and a control circuit 23. The LCD driver LSI chip 21 or LCD driver LSI is electrically connected to terminal electrodes of the LCD panel through an anisotropic conductive film. To such a configuration, a backlight unit 38 is attached, and chassis 4 completes the module structure.

FIG. 2 is a conceptual diagram illustrating a cross-section of the LCD panel 1. A liquid crystal layer (LC layer) 13 is formed in a space between the TFT substrate 11 and the CF substrate 12. A size of the space is approximately 3 to 5 μm and controlled by the arrangement of spacers 14 inside the panel. The liquid crystal layer is in a liquid state and sealed with surrounding sealing 15. In the liquid crystal layer, the arrangement of liquid crystal molecules is controlled so that they function as an optical crystal. The liquid crystal molecules are arranged vertically or horizontally with respect to interfaces that are inner faces of the substrates. This arrangement is called an orientation.

Oriented films 17 are coated onto the inner faces of the TFT substrate 11 and the CF substrate 12, i.e., on the liquid crystal layer sides. Further, polarizer films 18 and 19 are placed on the outer faces of the TFT substrate 11 and the CF substrate 12. On the TFT substrate 11, a TFT 111, a holding or a storage capacitor (Cs) 112, and a pixel electrode 113 are arranged. The combination of the TFT 111, the holding capacitor 112, and the pixel electrode 113 is a basic configuration of one pixel. Several million pixels are arranged in one LCD panel. Therefore, such pixels are connected in a matrix form through wiring on the TFT substrate 11.

The opposite CF substrate 12 is comprised of a black matrix (BM) 121, a color filter (CF) 122 consisting of three primary colors (red, green, and blue), and a common electrode 123. The common electrode 123 is typically placed on the CF substrate side, however, in an IPS liquid crystal (In-Plane Switching Nematic Liquid Crystal) mode, it is placed on the TFT substrate 11. A schematic diagram of the IPS liquid crystal is shown in FIG. 3.

In FIG. 2, the common electrode 123 is a transparent electrode, and uses indium tin oxide (ITO) or indium zinc oxide (IZO). In order to lead it outside, it is led to the TFT substrate 11 through a short part 161. Each electrode is electrically connected to the driving circuit 2 through a connection pad 162. Also, the TFT substrate 11 and the CF substrate 12 require transparency to light, and use hard glass. See U.S. Pat. Nos. 2,701,698 and 5,598,285 for more information on the IPS liquid crystal as shown in FIG. 3.

FIG. 4 is a plan view, a cross-sectional view, and an equivalent circuit diagram of a pixel part 31 and a TFT part 32. Each pixel is connected to gate wiring 33 and signal wiring 34. Accordingly, as shown in the plan view of FIG. 4, the TFT part has three kinds of electrodes, i.e., a gate electrode 351, a source electrode 352, and a drain electrode 353. The drain electrode 353 is connected to the pixel electrode 113 via a through-hole.

As can be seen from a cross-sectional view in FIG. 5, amorphous silicon (a-Si) 36 is used as semiconductor, and silicon nitride SiN_(X), a silicon oxide film SiO_(X), a multilayered film of them, or an organic material layer is used as a gate insulation film 37. Expressing each pixel part as the equivalent circuit diagram (FIG. 6) results in the additions of parasitic capacitors C_(gs), C_(gd), and C_(ds) between respective electrodes of the TFT. A liquid crystal layer is arranged between a pixel electrode 113 and a common electrode 123 on an opposite substrate, and expressed as C_(lc) in the equivalent circuit diagram. Parallel to C_(lc), a storage capacitor C_(s) is formed.

FIGS. 7, 8, and 9 show three kinds of a-Si TFT structures, i.e., a staggered top gate structure, an inversely staggered channel stopper structure, and an inversely staggered channel etch structure. Among them, the channel etch structure shown in FIG. 9 is often used in practice.

An embodiment applied to gate wiring of a TFT is now described. The inversely staggered channel etch structure is often used for an a-Si TFT. In such a case, a gate electrode is formed by sputtering on a glass substrate, and a pattern is formed by wet etching.

In this case, as shown in a cross-sectional view of FIG. 10, the structure has a tapered shape for reducing mechanical stress. A TFT structure in which CuMn, which is one of copper alloys, is used as a gate electrode is provided. For a glass substrate, alkali-free glass is used. One example of alkali-free glass composition is shown below.

Component Rate of Content (%) SiO₂ 49.0 Al₂O₃ 11.0 B₂O₃ 15.0 Metal (e.g. Fe) 25.0 Alkali —

Next, onto the glass substrate, a CuMn thin film is formed by sputtering CuMn alloy. A thickness of the film is approximately 200 nm. The substrate is then thermally treated in a slightly oxidizing atmosphere, or in an inert gas atmosphere, such as pure argon containing oxygen as an inevitable impurity, at 200 to 450° C. or higher for 3 minutes to 50 hours. Consequently, Mn is diffused in Cu and forms an oxide layer 45 having a thickness of 1 to 10 nm at an interface with the glass and on a surface of the CuMn thin film.

At the interface between the gate electrode 351 and the glass substrate 11, additive is diffused and reacts with SiO₂ in the glass, and the resulting oxide becomes (Cu, Mn, Si)O_(X). This oxide ensures adhesiveness between the gate electrode and the glass substrate. Further, (Cu, Mn, Si)O_(X) which is an oxide can function to prevent Cu diffusion into the glass, and prevent oxidation of a wiring material etc. by the formation of the oxide film having high adhesiveness to the substrate.

On the other hand, the CuMn film surface reacts with oxygen in the atmosphere to thereby form an oxide layer (Cu, Mn)O_(X) having a thickness of a few nm. Subsequently, the gate electrode is patterned by wet etching, and both ends of the electrode are tapered. Further, a thermal treatment is performed on it at 200 to 450° C. in a slightly oxidizing atmosphere, or in an inert gas atmosphere, such as pure argon containing oxygen as an inevitable impurity, to thereby form an oxide layer 45 as well.

Another method for forming an oxide layer is now described. Following the formation of a gate electrode, three layers of SiN/a-Si/n⁺ a-Si, which are to be a gate insulation film and a semiconductor film, are continuously deposited by plasma CVD. At this time, a substrate temperature is 300 to 350° C., which is high enough for a thermal treatment. Accordingly, when a substrate is loaded into a plasma CVD apparatus, an oxide layer 45 can be formed in a slightly oxidizing atmosphere at the substrate temperature of 300 to 350° C. At an interface with a glass substrate, an oxide layer similar to the above is formed.

On the other hand, the oxide layer 45 formed at an interface between the gate electrode and the gate insulation film eventually becomes (Cu, Mn, Si)O_(X). The oxide layer 45 can ensure adhesiveness between the gate electrode and the gate insulation film, and prevent Cu diffusion into the gate insulation film. The gate insulation film is sometimes made of SiOn, and in such a case, Mn diffused in CuMn reacts with oxygen in the gate insulation film to thereby form an oxide layer 45. The oxide layer 45 in this case eventually has a composition similar to that mentioned above.

As described above, Mn in the CuMn alloy is diffused into and fixed in the oxide layer 45, and therefore the gate electrode comes close to pure Cu. Compared with pure Cu having a resistivity of 1.7 μΩ·cm, the alloy having a resistivity of 2.2 μΩ·cm was obtained when it was thermally treated at 200 to 250° C. in a slightly oxidizing atmosphere. This value is sufficiently lower than resistivity of Al. Because most of Mn in the CuMn thin film escapes during the thermal treatment and forms an oxide layer, a main body of wiring can achieve resistivity close to that of the pure copper.

The gate electrode forms gate wiring in such a state, and therefore it reduces a propagation delay of a gate voltage pulse, whereby unevenness in brightness of an LCD due to shading can be decreased.

This embodiment is characterized by applying a novel copper alloy, i.e., CuMn, to a gate electrode or gate wiring held between a glass substrate and a gate insulation film, i.e. different kinds of insulation layers; forming an oxide layer 45 to cover the electrode; preventing Cu diffusion into the glass substrate and the gate insulation film, both of which are adjacent insulation layers; and ensuring adhesiveness to the adjacent insulation layers.

This enables to form an oxide film having high adhesiveness to a substrate and to prevent oxidation of a wiring material and the like, as well as to provide a liquid crystal display device equipped with wiring, an electrode, or a terminal electrode having high conductivity.

Further, the copper alloy CuMn used as the gate electrode and the gate wiring comes into a state close to pure copper by Mn diffusion into the coating oxide layer 45. That is, the gate electrode and the gate wiring of the present invention enable to provide low resistivity close to that of the pure copper. In addition, it is only necessary to form as a single layer of the CuMn layer providing a gate insulation film, and by the formation of the coating oxide layer 45, the low resistivity close to that of the pure copper can be provided, and shading of images can be reduced.

Further, although in conventional Cu wiring, three layers of Cu alloy/pure Cu/Cu alloy are deposited, it is only necessary in the present invention to deposit a single layer of CuMn alloy, which can reduce film formation steps, resulting in a significant advantage in cost reduction.

Because of such features, the liquid crystal display device of the present invention enables to prevent oxidation of a wire material and the like by the formation of the oxide film having high adhesiveness to the substrate, and the present invention enables to provide the liquid crystal display device using feasible copper wiring.

[Copper Alloy]

An additive element in the copper alloy applied to the liquid display device of the present invention will be described below. The additive element in the copper alloy applied to the gate wiring 33 and the gate electrode 351 in the TFT-LCD regarding the liquid display device of the present invention is a metal that has oxide formation free energy with negative value larger than that of Cu and a diffusion coefficient of the additive element in Cu (hereinafter referred to as a “diffusion coefficient” unless otherwise noted) larger than a self-diffusion coefficient of Cu.

By selecting the additive element of which the diffusion coefficient is larger than the self-diffusion coefficient of Cu, the additive element can reach the Cu surface faster to preferentially form an oxide film layer comprising the additive element on the Cu alloy surface.

In other words, if the diffusion coefficient of the additive element is smaller than the self-diffusion coefficient of Cu, the additive element requires a significant amount of time to reach the Cu alloy surface, and therefore a Cu oxide film layer consisting of CuO, Cu₂O, and the like is formed on the Cu alloy surface.

In this case, because the Cu oxide film layer is not robust, oxygen intrudes into the inside of the Cu oxide film layer and forms oxide of the additive element in the Cu alloy. In addition, an amount of Cu in a metal state decreases as the oxidation of Cu progresses, and if such Cu alloy is used for wiring of a liquid crystal display device, its electrical resistance would be increased.

Accordingly, the copper alloy applied to the present invention was intended to provide a solution to such a problem by the selection of the additive element of which the diffusion coefficient is larger than the self-diffusion coefficient of Cu.

The additive element in the copper alloy, which is applied to the present invention, is now described in detail. It is preferable that the additive element in the copper alloy forms a solid solution in an additive amount ranging from 0.1 to 25 atomic % in the Cu alloy. This is because the additive element cannot be easily diffused if it is not within the solid solution range in the Cu alloy. Especially, if the additive element forms an intermetallic compound with Cu, it is hardly diffused.

Also, if the additive amount of the additive element in the Cu alloy is lower than 0.1 atomic %, the oxidation of Cu cannot be prevented because the oxide film layer to be formed becomes thin. On the other hand, if the additive amount of the additive element exceeds 25 atomic %, the additive element is sometimes precipitated as a secondary phase.

Specifically, the additive element in the Cu alloy applied to the present invention is at least one of elements selected from the group consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd. A single element may be used, or a plurality of additive elements may be applied together. Manganese (Mn) is especially preferable. Into the Cu alloy, an impurity such as S, Se, Te, Pb, or Si may be inevitably mixed in, however, this is acceptable as long as characteristics of the Cu alloy including electrical conductivity and tensile strength are not deteriorated.

In the present invention, a method for forming the Cu alloy is not particularly limited. That is, a plating method such as electric field plating or molten plating, or a physical vapor deposition method such as vacuum evaporation or sputtering may be used. The Cu alloy deposited by any of the methods is thermally treated to form an oxide film layer.

Temperature for the thermal treatment is, for example, 150 to 450° C., and a time period for the thermal treatment is, for example, in a range of 2 minutes to 5 hours. If the thermal treatment temperature is lower than 150° C., productivity is reduced because the formation of the oxide film is time-consuming. On the other hand, if it exceeds 450° C., it causes a problem that Cu is oxidized to form an oxide film before an additive element in the Cu alloy is diffused to and reaches a surface. Also, if the thermal treatment time period is shorter than 2 minutes, thickness of the oxide film is too thin, while if it exceeds 5 hours, the formation of the oxide film is too much time-consuming.

One example providing low resistivity in one of the copper alloys used in the present invention, CuMn, is now described. By the thermal treatment, CuMn constitutes wiring or an electrode, and an oxide film layer covering it. An example of a relationship between the thermal treatment time period (second) and resistivity (μΩ·cm) of the wiring body is shown in FIG. 11, using oxygen concentration (ppm) in a thermal atmosphere as a parameter.

Measurements in FIG. 11 were carried out in such a way that Cu and Mn containing oxide was first formed also in a surface layer portion on the top side of the wiring body, then the oxide layer in the top surface layer portion was removed to expose the Cu wiring body, and the electrical resistivity of the Cu wiring body was measured. According to the result, the resistivity of the Cu wiring body was extremely low, and 2.2 μΩ·cm under the conditions of an oxygen concentration of 50 ppm and a thermal treatment time period of 4 minutes. This value was close to an electrical resistivity of 1.7 μΩ·cm of a pure Cu bulk material. That is, a satisfactory value to provide low resistive wiring and to promote an image quality improvement in a TFT-LCD was realized.

Similarly, FIG. 12 shows an example of relative resistivity against thermal treatment temperature using a thermal treatment time period as a parameter. It turns out that the resistivity is saturated to low resistivity at a thermal treatment temperature of 150 to 400° C. and a thermal treatment time period of approximately 2 minutes. The time period is short enough for processing time, and is an adequate value for manufacturing a TFT-LCD.

[Shading]

Among improvements of image quality obtained by lowering wiring resistance, which are remarkable effects of the present invention, a shading reduction effect will be described below. First, an operation of a TFT-LCD is described in detail. A display device used in the present invention is an LCD in which pixels are arranged in a matrix form. This LCD is called an active matrix LCD (AM-LCD).

For example, in the case of a TFT-LCD for a digital TV, the number of pixels in a full HD specification is (1920×3)×1080. That is, the number of scanning lines is 1080, and the number of signal lines is 5760 because one pixel consists of three primary colors (red, green, and blue) and therefore the number of pixels in a horizontal direction is tripled. In this TFT-LCD, gate voltage V_(G) shown in FIG. 13 is applied to a gate electrode of the TFT constituting the pixel. Typically, V_(G) is 10 to 15 V.

On the other hand, signal voltage V_(S) is applied to a source electrode, and a gate voltage pulse serves as a scanning signal. Given that a frame frequency to display one screen is 60 Hz, a frame time is 16.7 ms. If the 1080 scanning lines are scanned in a line sequential scanning mode, a gate voltage pulse width becomes approximately 16 μs.

As illustrated in FIG. 13, a cycle of the gate voltage pulse is 16.7 ms, and the pulse width is approximately 16 μs. On the other hand, given that a LCD drive voltage V_(lC) is approximately 5 V, the signal voltage applied to the source electrode to drive a liquid crystal is approximately 10 V that is a double of the voltage amplitude. A difference between the signal voltage and a common voltage V_(com) applied to the common electrode provides liquid crystal layer drive voltage V_(p) (t), and FIG. 13 exemplifies a driving waveform in a frame inversion system in which a polarity of V_(p) (t) is inverted for each frame to transform it into alternating voltage.

In this case, transmittance of the LCD modulates brightness of the display by voltage modulation of the signal voltage. Further, the liquid crystal drive voltage is retained while the gate voltage pulse is off (approximately 16 ms that substantially corresponds to the frame time).

FIG. 13 illustrates such situation. The liquid crystal layer drive voltage consists of a writing state and a holding state. Also, the transmittance of the LCD depends on a root-mean-square (r.m.s.) value of the liquid crystal layer drive voltage V_(p) (t). For this reason, the LCD drive voltage V_(lc) is expressed by the following equation:

$\begin{matrix} {{\left\langle {Vlc} \right\rangle{rms}} = {\frac{1}{2{Tf}}\sqrt{\int_{t = 0}^{2{Tf}}\left\{ {{{Vp}( + )} - {Vcom}} \right\}^{2}}{\mathbb{d}t}}} & (1) \end{matrix}$ Meanwhile, switching time of the a-Si TFT is of the order of μs because capacitance loads are driven and mobility of a-Si is as low as 0.3 to 1.0. Accordingly, a few μs is required for switching-on of the TFT during the gate voltage pulse width of 16.7 μs.

Further, because the liquid crystal layer is a capacitance load, an application of the signal voltage is delayed. As a result, rise of the liquid crystal layer drive voltage V_(p) (t) is also delayed. In addition, in a TFT-LCD for TV with a full HD specification, 5760 pixels are arranged in one line. A plurality of TFTs arranged in one line are simultaneously excited by applying the gate voltage pulse to an end part of the gate wiring.

At this time, the gate voltage pulse is propagated from the end part to gate electrodes of respective pixels. A propagation speed decreases as a resistance value and parasitic electrical capacitance of the gate wiring are increased. This phenomenon is referred to as a propagation delay of the gate voltage pulse. As the propagation delay becomes larger, adequate time to input the liquid crystal layer drive voltage cannot be obtained, and therefore the liquid crystal drive voltage for each pixel cannot reach a predetermined value. As a result, the transmittance of the liquid crystal layer becomes uneven, i.e., the screen brightness becomes uneven, causing the shading. It should be appreciated that also in the above-described IPS liquid crystal and VA liquid crystal, it may cause the shading in the same manner.

A model of the propagation delay of the gate voltage pulse described above is shown in FIG. 14. Each pixel on the gate wiring can be equivalently expressed using resistance R and parasitic capacitance C. An RC delay of the gate voltage pulse in the each column is accumulated, and at a terminal node n5760, the propagation delay reaches several μs.

If a distribution of the LCD brightness at this time is schematically illustrated, the brightness is gradually varied along the gate wiring in a normally white mode LCD, and at the terminal, the screen is bright instead of black originally intended due to insufficient liquid crystal layer drive voltage. Therefore, the propagation delay of the gate voltage pulse is reduced by lowering the gate wiring resistance. Consequently, the unevenness in the screen brightness, in other words, the shading can be suppressed.

The present invention enables to reduce such shading by using the above-described copper wiring close to pure copper, as illustrated in FIG. 14.

[Adhesiveness to Glass]

Adhesiveness to glass that is another remarkable effect of the present invention is now described. Thin film wiring and electrodes formed from the copper alloy CuMn are covered with the oxide layer formed by the thermal treatment.

In a liquid crystal display device, such wiring and electrodes essentially require to have excellent adhesiveness to a glass substrate and the insulation layer. The adhesiveness is typically determined by performing a tape test. As shown in Table 1, if pure Cu thin film is formed on an insulation film SiO₂, sufficient adhesiveness cannot be obtained, causing separation.

TABLE 1 Table 1 Tape test results of Cu and Cu/Mn double layered film on an insulation film SiO₂ Material Thermal treatment temperature (° C.) (thickness: nm) 150° C. 200° C. 250° C. 300° C. 350° C. 400° C. 450° C. Cu(150 nm) X X X X X X X Cu(150)/Mn(2)stacked layer Δ ◯ ◯ ◯ ◯ ◯ ◯ Cu(150)/Mn(20) stacked layer Δ ◯ ◯ ◯ ◯ ◯ ◯ ◯: Good adhesiveness X: Separation (poor adhesiveness) Δ: Partial Separation

On the other hand, in a case of a double-layered thin film of Cu and Mn, interdiffusion of Cu and Si occurs at an interface between them by a thermal treatment, and an oxide layer having a composition of Cu_(X)Mn_(Y)Si_(Z)O (0<X<Y, 0<Z<Y) is formed at the interface. This enables excellent adhesiveness to the insulation layer SiO₂ to be obtained.

As the tape test to evaluate the adhesiveness, a separation state was evaluated when a tape was peeled off after the tape had been stuck on a Cu thin film surface. Before the tape is peeled off, it is bonded onto the surface by pressing with a nail.

This procedure is repeated 10 times on a same position of the thin film to check the adhesiveness to a substrate. Results of the tape test were analyzed in detail.

According to the results, the CuMn double-layered thin film exhibited low electrical resistivity by being thermally treated at 200° C. or higher. On the other hand, regarding the adhesiveness, partial separation was observed when the film was thermally treated at 150° C. By a thermal treatment at 250° C., excellent adhesiveness was exhibited in all the conditions that thermal treatment time periods are 3 minutes, 30 minutes, 1 hour, 20 hours, and 100 hours. Similarly, excellent adhesiveness was obtained when the thermal treatment temperature was 350° C.

FIG. 15 shows interface adhesion strength in case of thermally treated Cu-4atomic % Mn alloy at 400 degree/C. for 30 minutes after forming in film on SiO2 substrate, comparing with in case of forming Ta frequently used for semiconductor wiring, between pure Cu and SiO2. The adhesion strength is measured by a nano scratch method. A horizontal axis indicates scratch time required to scan a length of 6 μm on the film surface. A smaller time corresponds to a faster scratch speed. At any scratch speed, the load value required for interface separation is larger in Cu—Mn/SiO2 compared to Cu/Ta/SiO2, showing high adhesion strength.

The oxide layer constituting the interface with the wiring and the electrodes on the insulation film SiO₂ has the composition of Cu_(X)Mn_(Y)Si_(Z)O as shown in FIGS. 16 and 17, and is amorphous. As described, at the interface, the oxide layer containing mainly Mn act as an excellent diffusion barrier to prevent interdiffusion between Cu and SiO2. The gradual concentration change near the interface of the oxide layer promote an excellent adhesion of the oxide layer with the Cu layer and with the SiO2 layer. It can be considered that this provides the excellent adhesiveness.

This enables the oxide film with high adhesiveness to a substrate to be formed to prevent oxidation of a wiring material or the like, and a liquid crystal display device having wiring, an electrode, or a terminal electrode with high electrical conductivity and a manufacturing method therefore to be provided. All of such difficulties are simultaneously overcome, and the wiring, electrode, or terminal electrode applicable to a practical manufacturing process can be formed.

In addition, Cu-4atomic % Mn alloy is formed in a film on the glass substrate using a spatter device in the current invention. Thereafter, the film is thermally treated in a pure argon atmosphere within a temperature range of 150-350 degree/C. The time required for the thermal treatment was 10 to 60 minutes. An evaluation (a tape test) is performed to find out whether the thin film strip off or not by peeling a piece of scotch tape adhered to the alloy thin film surface for both specimens with or without thermal treatment after forming a film. As a result, the alloy thin film without thermal treatment separated from the glass substrate. On the other hand, as shown in FIG. 19, when thermally treated for over 20 minutes in temperature of 200 degree/C. or above, or over 10 minutes in temperature of 250 degree/C. or above, the alloy thin film was adhered to the glass substrate. Similar tape test has been done to pure Cu thin film, however, separation occurred to all heat treatment conditions. Based on this, it became apparent that favorable adhesiveness to glass substrate was presented by thermally treating in temperature of 200 degree/C. or above using Cu—Mn alloy.

FIG. 18 shows a cross-section TEM image after thermally treating Cu—Mn alloy at 250° C. for 10 minutes. Top is the Cu—Mn alloy thin film portion and bottom is the glass substrate. A reaction layer having even contrast is observed along an interface of both layers. As a result of analysis using an X ray energy dispersive spectroscopy (XEDS) device attached to TEM, the reaction layer along the interface turned out to be an oxide mainly composed of Mn. Forming of this oxide is the reason for improvement in adhesiveness of the interface.

In order to decrease resistivity, it is ideal to add only enough Mn to sufficiently form the interface layer. For example, when thermally treating 200 nm alloy film at 250 degree/C. for 10 minutes, an interface layer with 6 nm thickness is formed. Amount of Mn contained in the interface layer is approximately 50%, it is equivalent to a pure Mn layer of approximately 3 nm in thickness existing. Therefore, Mn concentration to be added to the alloy is Mn of 3 parts of 200 in volume ratio, thus Cu (1-2) atomic % Mn is ideal considering the density of Cu and Mn. When the thickness of the alloy film is 100 nm, twice the Mn concentration is required, and when the thickness of alloy film is 300 nm, 1.5 times the Mn concentration is required.

Also, FIG. 19 shows the result of adhesiveness evaluation by tape test after thermally treating Cn—Mn alloy formed in film on glass substrate at each temperature for predetermine time. In this figure, X indicates separation occurred, Δ indicates separation occurred in some cases, ◯ indicates separation did not occur at all. In addition, separation occurred for pure Cu in all conditions. Based on FIG. 19, no separation occurred for the present invention in case of 250 degree/C. or above.

In addition, in case of alloy with more than sufficient amount of Mn is added to form an interface layer, heat treatment should be done in a high purity Ar gas (oxygen concentration of 0.1 ppm or below) atmosphere contains oxygen as inevitable impurity. FIG. 20 shows resistivity of alloy thin film on the glass when thermally treated at 350 degree/C., and the time evolution of Mn-oxide thickness formed on the surface. As shown in FIG. 20, Mn remaining in the alloy film after forming an interface layer can be discharged from the alloy film by reacting with oxygen of less than 0.1 ppm contained in pure Ar and forming an oxide on the surface. As shown in FIG. 20, it became apparent that the resistivity decreases as the Mn oxide layer on the surface grows in thickness. Resistivity after 30 minutes of heat treatment decreases to a value equivalent to pure Cu thin film. XEDS analysis of the Mn concentration indicated no Mn in the alloy film, which revealed that excess Mn can be discharged from alloy film completely.

[Manufacturing Process]

Regarding the liquid crystal display device according to the present invention, the oxide layer associated with the copper alloy used as a wiring and electrode material of a TFT-LCD, and a manufacturing process of the oxide layer are described below.

FIG. 21 shows the fundamentals of a TFT manufacturing process. Thin films 51 of metal, semiconductor, and insulator are respectively deposited, and they are patterned by photo-etching using mask 52 and regist 53. Sputtering is used for the metal film deposition, and CVD (Chemical Vapor Deposition) is used for the semiconductor and insulator depositions. For etching, either dry or wet etching is used. The wet etching is often used for the metal to form into the wiring. These steps are repeated four to five times to manufacture a TFT.

Among them, FIG. 22 shows a five-mask process that uses five kinds of photomasks for exposure. The process sequence comprises the steps of: (1) forming a gate pattern by wet etching using a mask 1; (2) simultaneously processing three layers of SiN/a-Si/n⁺ a-Si by dry etching using a mask 2 to form a pattern; (3) forming a source/drain electrode pattern by wet etching using a mask 3; (4) fabricating the n⁺ a-Si layer into a channel structure by dry etching using the mask 3; (5) patterning the SiN passivation film using a mask 4; and (6) patterning an ITO (Indium Tin Oxide) film, which is a transparent electrode, using a mask 5. This allows a TFT substrate to be manufactured.

FIG. 23 shows a cross-section of a structure of a TFT manufactured by a standard five-mask process. As illustrated in FIG. 24, a gate terminal part constituting an external electrode has a stacked structure of a metal thin film and an ITO film. FIG. 25 shows a plan view of each pixel.

Selecting an additive element in the copper alloy according to the present invention such that the element has oxide formation free energy with negative value larger than those of elements of an oxide layer enables an oxide film layer to be formed through reduction of the above-described oxide. Besides, in an oxidative atmosphere, the oxide film layer can be formed without the reduction of the oxide.

Further, if the Cu alloy applied as a wiring and electrode material in the TFT-LCD of the present invention is brought into contact with an insulation film containing oxygen, the additive element in the Cu alloy is diffused to the interface and thereby the additive element is oxidized to form the oxide film layer.

Still further, metal elements in the insulation layer, and Cu and the additive element in the Cu alloy form oxides respectively, and these oxides are combined together to form a compound oxide film. For example, if a TFT substrate contains oxide such as SiO₂, and gate wiring inside the Cu alloy provided on the substrate is thermally treated, the additive element in the Cu alloy forming the gate wiring is diffused to an interface between the substrate and the gate wiring and reacts with oxygen in the substrate to form into oxide, which forms an oxide film layer.

Also, for example, a gate insulation film 37 consisting of SiNO or the like is provided on a gate electrode 21, and by applying a thermal treatment in the manufacturing process, an oxide layer expressed by (Cu, Si, additive element)O_(X) is formed at an interface between the gate electrode 351 and the gate insulation film 37. In this way, the oxide layer can be provided on a surface of Cu alloy by using the Cu alloy as a wiring and electrode material for a TFT-LCD.

A method for manufacturing a liquid display device according to the present invention is provided. The manufacturing process of a TFT substrate of the TFT-LCD according to the present invention comprises a step of depositing copper alloy on a substrate by physical evaporation or chemical vapor deposition, which mainly consists of Cu and forms an oxide layer of an additive element to said Cu on the Cu surface or at an interface with the substrate; and a step of photo-etching the obtained copper alloy film to form at least one of each wiring or each electrode.

In this case, the additive element in the above copper alloy is preferably at least one type of metal selected from the group consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd. Also in this case, a step of forming an oxide layer on a surface of at least one of the formed wiring or electrode may be included.

Also, an oxygen concentration in atmosphere gas used in the above-described oxide layer formation step is preferably an inert gas such as argon containing oxygen no less than 1 ppm and no more than 100 ppm. Alternatively, argon gas containing oxygen as an inevitable purity may also be used. Further, the oxide layer formation step may be a step of forming at least one of the wiring or electrode and then heating at 150 to 400° C. for 2 minutes to 50 hours to form an oxide layer of the additive element in the copper alloy on the surface of at least one of the wiring or electrode.

A thin film of an alloy was deposited on an insulation film SiO₂ using Cu-2 atomic % Mn alloy comprised of Cu with a purity of 99.9999% and Mn with a purity of 99.98% as a target material, and thermally treated at a temperature not less than 150° C. and not more than 450° C. Subsequently, a depth compositional profile was analyzed from a surface of the thin film using Auger electron spectroscopy.

Also, a cross-sectional sample was prepared, and a cross-sectional photograph thereof is shown in FIG. 26. Further, structural observation and compositional analysis were carried out using a transmission electron microscope and X-ray energy-loss spectroscopy (EELS). One example of the results is shown in FIG. 27. A stable oxide layer that contains Mn as a main element and has a thickness of a few nm to 20-odd nm is formed around an interface between the Cu—Mn alloy and the insulating substrate and around a surface of the Cu—Mn alloy.

FIG. 28 shows a variation in film thickness of the oxide layer against a thermal treatment time period. Table 2 shows a film thickness of the obtained oxide layer against Mn atomic concentration in the CuMn alloy, a thermal treatment time period, and thermal treatment temperature. FIGS. 16 and 17 shows an enlarged view of a compositional distribution of the oxide layer. The distribution in which Mn has a peak around a center of the oxide film is exhibited. Cu intrudes from the wiring body to the oxide layer; however, the Cu intrusion into the insulation film is prevented.

TABLE 2 Table 2 Thickness of formed oxide film layer Thermal Atomic treatment concentration in temperature CuMn alloy Thermal treatment (° C.) (at · %) time (minute) 350° C. 450° C. 10% 20 min 3.2 nm 6.1 nm 20% 30 min — 8.2 nm

Requirements for a sputtering target are provided in case that CuMn is used as the copper alloy in the liquid crystal display device of the present invention. In a TFT-LCD of the present invention, a propagation delay in gate wiring is particularly large. In order to reduce the delay, it is preferable to use copper wiring to provide wiring having low resistance close to that of pure copper, as described above.

FIG. 29 shows a cross-sectional view of gate wring using CuMn. The gate wiring is comprised of a wiring body 171 and an oxide film layer 172. Parameters a, b, h, t₁, and t₂ in FIG. 29 represents sizes of respective parts. a and b are a few μm to 10-odd μm, and h is 200 to 500 nm. t₁ and t₂ are 2 to 10 nm. In this case, in order for the wiring body 171 to provide low resistivity close to that of pure copper, an amount of Mn corresponding to that contained in the oxide film layer 172 formed by a thermal treatment is preferably contained in the wiring body 171, CuMn, before the thermal treatment. Accordingly, a content of Mn that is an additive element contained in the sputtering target is provided.

[Organic EL]

The present invention is not limited to a TFT liquid crystal display device, but applicable to an organic EL display device. One example of organic EL according to the present invention is illustrated in FIG. 30. It is mainly comprised of a glass substrate 201; an anode (ITO) 202, a hole transport layer (HTL) 203, an emission layer (EML) 204, and an electron transport layer (ETL) 205, which are sequentially stacked on the glass substrate 201; and a cathode 206 arranged on the electron transport layer 205. For the emission layer, an organic matter such as a diamine system is used. The anode 202 and the cathode 206 are electrically connected to each other with an electrode line through a power supply. Each of the layers has a thickness of, for example, approximately a few tens nm.

The organic EL display device comprises a scanning line 194, a signal line 195, and a power line 196, which intersect with one another in a matrix form, and a pixel area 198 surrounded by the scanning line 194, the signal line 195, and the power line 196, and as one example, the pixel area 198 has an organic EL element 191, a driving TFT 192, and a switching TFT 193.

The organic EL comprises the anode, the hole transport layer, the organic emission layer, the electron transport layer, and the cathode, which are stacked on the glass substrate. One pixel is comprised of a TFT circuit and the organic EL element, and a plurality of pixels are arranged in a matrix form, which is a so-called active matrix organic EL display device.

An equivalent circuit of one pixel is shown in FIG. 31. Also, FIG. 32 shows a cross-sectional view of the pixel. For example, on a glass substrate 181, there are a driving TFT part 182 and an organic EL element 184, in which electrodes 183 for a TFT, a cathode 185 made of metal, and a transparent electrode 186 are present, and in this example, light 187 is emitted toward a lower part of the substrate.

In the active matrix organic EL display device, unevenness of an image caused by a propagation delay of a gate voltage pulse generated in an active matrix liquid crystal display device occurs. To deal with it, copper alloy is used as a wiring material having high conductivity.

The copper alloy of the present invention is useful for a scanning line and a signal line. In the organic EL display device according to the present invention, at least one of the scanning line, the signal line, the power line, or the TFT electrode uses copper as a main component, and consists of copper alloy that forms an oxide layer of an additive element to Cu, which covers wiring or the electrode. A cross-section of the wiring is a structure such as FIG. 29.

Further, regarding the copper alloy, copper alloy in which an additive element is diffused to a surface of the copper alloy to form an oxide film layer of the additive element may be used. Still further, the additive element may be at least one type of metal selected from the group consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd. Still further, the additive element is preferably Mn.

The present invention brings electrical resistivity of wiring or an electrode close to that of pure copper, leading to low resistivity, and prevents oxidation of Cu at a surface of the wiring, as well as enables to provide a liquid crystal display device having copper alloy wiring or electrode onto which oxide film layer with excellent adhesiveness to a substrate is formed, and suppress unevenness of an image caused by a propagation delay of a gate voltage pulse. Also, it can reduce wiring and electrode fabrication steps and contribute to simplification of a TFT process, and an effect on reduction in manufacturing cost can be expected. Further, the present invention brings about similar effects to an organic EL display device. 

1. A liquid crystal display device comprising a gate wire or a gate electrode formed on a substrate on a Thin Film Transistor (TFT) side of a TFT liquid crystal display device, wherein the gate wire or the gate electrode has a structure of being held between at least two different insulation layers or insulators, and the structure is comprised of a first layer including copper and a second layer consisting of an oxide covering an outer circumferential part of the first layer, wherein, the second layer has a compositional formula of Cu_(X)Mn_(Y)Si_(Z)O (0<X<Y<, 0<Z<Y).
 2. The liquid crystal display device according to claim 1, wherein the first layer is formed from a copper alloy, and an additive element in the copper alloy is at least one type of a metal selected from the group consisting of Mn, Zn, Ga, Li, Ge, Sr, Ag, In, Sn, Ba, Pr, and Nd and a combination of two or more thereof.
 3. The liquid crystal display device according to claim 1, wherein the first layer is formed from a copper alloy, and an additive element in the copper alloy is Mn.
 4. The liquid crystal display device according to claim 3, wherein an additive amount of said Mn is in a range of 0.5 to 25 atomic %.
 5. The liquid crystal display device according to claim 1, wherein the second layer is an oxide layer comprising Mn mainly and Cu subsidiary.
 6. The liquid crystal display device according to claim 1, wherein the insulation layer comprising said wire or said electrode, or the insulation film includes a glass element.
 7. The liquid crystal display device according to claim 1, wherein the insulation layer comprising said wire or said electrode, or the insulation film is any one selected from the group consisting of SiN_(X), SiO_(X), and SiO_(X)N_(Y)and a combination of two or more thereof.
 8. The liquid crystal display device according to claim 1, wherein the second layer contains Cu and Si.
 9. The liquid crystal display device according to claim 1, wherein the second layer has a thickness of 1 to 30 nm.
 10. The liquid crystal display device according to claim 1, wherein a common electrode is formed on the TFT substrate side on which the gate wire is formed.
 11. A liquid crystal display device being a Thin Film Transistor (TFT) liquid crystal display device comprising a liquid crystal material held between a pair of substrates, wherein a gate wire or a gate electrode formed on a side of a TFT substrate of the pair of substrates has a wiring structure consisting of at least two different insulation layers containing Si, with one of the two different insulation layers comprises Cu and Mn, and the other insulation layer comprises a compositional formula of Cu_(X)Mn_(Y)Si_(Z)O (0<X<Y, 0<Z<Y), and the wiring structure is formed in a shape in which one of the insulation layers in the wiring structure is covered with the other insulation layer.
 12. The liquid crystal display device according to claim 11, wherein one of the insulation layers in the wiring structure is an oxide layer containing Mn mainly and Cu subsidiarily.
 13. The liquid crystal display device according to claim 11, wherein the second layer has a thickness of 1 to 30 nm.
 14. The liquid crystal display device according to claim 11, wherein a common electrode is formed on a TFT substrate side on which the gate wire or the gate electrode is formed.
 15. An organic Electro Luminescent (EL) display device, wherein a scanning line formed on a substrate of the organic EL display device has a structure of being held between at least two different insulation layers or insulators, and the structure is comprised of a first layer that includes copper and a second layer comprising an oxide covering an outer part of the first layer.
 16. The organic EL display device according to claim 15, wherein a compositional formula of the second layer is Cu_(X)Mn_(V)Si_(Z)O(0<X<Y, 0<Z<Y).
 17. The organic EL display device according to claim 16, wherein the second layer is an oxide layer further containing Mn mainly and Cu subsidiarly. 